Upsampling is a widely debated topic.

I believe it imparts a substantial audible difference, but not in every system. As the Passband filters, and amplifier characteristics of Meridian gear are optimised from Speaker to System, the "M" difference is more noticeable, if you have a Meridian System. Upsampling helps in dejittering the internal computations, and producing a more linear phase response. This means the Clock speed is less of an obstacle, further... The Input filter and output filter do not need to be as sharp, and the frequencies all the way to 22K roll off smoothly.


Some wide bandwidth Amplifiers have a hard time with Upsampling, as the signal leaving the Meridian has a seemingly unlimited bandwidth -- you may find some amplifiers to choke on this feed.

This Said... The G products generally compute all processes in Quad speed,
and output Quad 176.4 to the analogue system but due to limitations in the signal path, DSP loudspeakers accept only Dual speed data samples 88.2.

Whether this is audible or not depends in large measure upon the pipeline after exiting the M gear.

In an analogue system the quad speed carries all of the way through to the Speaker crossover. (save what issues your amplifiers may have).
In a Digital System -- PCM carries 88.2 to the speaker.

Whether you hear this upsampling or not; The difference is still up to you.
I'll wager that if you own a G68, and set-up your system to "high-speed" output for the DVD input, and set the CD input to "High-speed" off, alternating these sources: A & B... the Upsampling will make a believer of you. And you will never listen to basic bandwidth again.
Upsampling imparts Higher peaks, grander scale to the audible picture, less capped High frequencies, Broader textures, and an overall wider taller,and deeper sound-stage.

Upsampling is a better mousetrap, as it allows more refined sound shaping with less errors, and a very simple way to remove sampling image and spurs in the audible band.

(Opinion)
However given the inherent flaw in Passive circuits... Playing M gear Quad speed into Passive Loudspeakers is a bit like Recording your CD's to Cassette, to listen to them on your iPod

-Bernie